Donald Trump's lawyers have opened their impeachment trial defence by saying the president "did absolutely nothing wrong."

Mr Trump's legal team said the president had broken no laws by asking Ukraine to investigate his political rival, Democratic nominee Joe Biden.

They accused Democratic prosecutors of excluding key evidence during the presentation of their case and urged the Republican-majority chamber to clear the US leader of the charges, including the accusation that he obstructed Congress.

The president's legal team will portray Mr Trump as an individual who is under attack from his political opponents who are set on overturning the 2016 presidential election.

His lawyers are expected to use an aggressive and varied defence, including an expansive view of presidential powers.

They look to put Mr Biden on the backfoot in a bid to throw him off in his Democratic presidential nomination.

White House counsel Pat Cipollone told the trial on Saturday: "They're asking you not only to overturn the results of the last election, but as I've said before, they're asking you to remove President Trump from an election that's occurring in approximately nine months.

"They're asking you to tear up all the ballots across this country on their own initiative."

Mr Schiff closed the Democratic case by methodically describing the charges leveled at the preisdent Mr Trump - that he abused his power by asking the Ukrainian President for politically-motivated probes of political rivals, as well as threatening to withhold military aid to the country, then obstructed the Congress investigation into the matter.

Adam Schiff is at the forefront of the Democratic-led impeachment.
Picture:
PA

Mr Trump's lawyers contend he was within his rights as president when he asked President Zelensky for the investigation.

In response to allegations that he invited foreign interference, defence lawyers have already argued it was no different from the Hillary Clinton campaign's use of a former British spy to gather opposition research on Mr Trump in 2016.

Given that Republicans hold a 53-47 majority in the Senate, and a two-thirds vote would be required for conviction, acquittal seems the most likely outcome.

Mr Trump's team began their legal arguments on Saturday but only a short hearing was planned, and they will continue their case on Monday.

The president is being tried in the Senate after the House impeached him last month on charges he abused his office by asking Ukraine for the probes at the same time the administration withheld hundreds of millions of dollars in military aid.

The second article of impeachment against Mr Trump accuses him of obstructing Congress by refusing to turn over documents or allow officials to testify in the House probe.